Settable fluidic flip-flop



Dec. 30, 1969 C. J. AHERN- 3,486,692

SET'I'ABLE FLUIDIC FLIP-FLOP- Filed June 4, 1968 Qhw\e% 5. Ahem.

INVENTOR.

United States Patent O US. Cl. 235201 4 Claims ABSTRACT OF THE DISCLOSURE A fluidic flip-flop device having two operating stages. The output of the first stage controls the output of the second stage such that one output pulse is generated for each two input pulses. The input control passages of the first stage are aligned with an additional pair of passages which intercommunicate the fluid interaction region of the first stage with the control region of the second stage to provide for the setting or resetting of the output of the second stage.

CROSS REFERENCE This invention is an improvement of the invention disclosed in applicants issued Patent No. 3,348,773, which is assigned to the assignee of the present invention- BRIEF SUMMARY OF INVENTION In the referenced patent, a fluidic flip-flop device is shown and described. In working with that device, I have found a need to be able to establish an initial output pulse from a particular output leg of the second stage in the absence of count pulses at the input of the first stage. Inasmuch as it is sometimes necessary to have output from one leg and sometimes from the other, the device could not intentionally be made asymmetric so as to condition initial output to select one of the possible paths available. External controls, on the other hand, add to the cost of the device and'increase its complexity. It is, therefore, an object of this invention to provide asymmetrical resettable fluidic flip-flop. It is also an object of this invention to provide a fluidic flip-flop in which set and reset may be accomplished without resort to complex external controls or to the use of a preestablished code number. It is a further object of this invention to provide a settable fluidic flip-flop which is low'in cost and easy to produce. It 'is also an object of this invention to provide alow impedance flow path for the set and reset control signals which does not alter the operational effectiveness of the device.

Although the concept of the referenced patent has proven successful, it is desirable to improve the device so that the switching levels of set and reset, whether in the presence or in the absence of the control signal input are nearly the same. It is, therefore, an object of the present invention to provide a flip-flop which may be set (or reset) in the absence of a control signal or count input. It is a further object of this invention to provide a flip-flop in which switching levels remain substantially unaffected by the presence or the absence of a control or count input signal Because devices of this nature have memory means operatively associated with the input or splitter stage, it is a further object of this invention to provide a settable fluidic flip-flop in which set pulses also provide for correction of the memory in the splitter stage. It is a further object of the present invention to provide a settable fluidic flip-flop having means to correct the memory of the splitter stage and which may be set in the absence of a count signal. It is a still further object of the present invention to provide a settable fluidic flipflop having the aforementioned advantages in which the switching levels remain substantially constant whether in the presence of a control signal or not.

BRIEF DESCRIPTION OF THE DRAWING The drawing shows a schematic embodiment of my invention having arbitrarily-designated set, reset, and control inputs.

DETAILED DESCRIPTION OF THE DRAWING The drawing shows the two-stage resettable fluidic flipflop, according to the present invention, with the first, or splitter stage, designated generally by 10, and the second, or output stage, designated generally by 12. The splitter stage 10 has set and reset inputs 14 and 16 and the count input 18 which meet at a fluid interaction area 20. Branchin off from the fluid interaction area 20 are four fluid conduits 22, 24, 26, and 28. Conduits 22 and 24 are arranged in an intercepting relationship with the set and reset passages 14 and 16 so that fluid flowing under pressure from either of them would, in the absence of how from the other two inputs, cross the fluid interaction area 20 and flow through the corersponding conduit 22 or 24. Splitter 29 is in line with the count passage 18 and downstream of the fluid interaction region 20, splitter 29 establishes the bifurcation between the two passages 26 and 28 which are slightly oflset from the center line of passage 18 on either side thereof and which are arranged to intercept fluid pulses from count passage 18 which may coincide with pulses from either the set or reset passages 14 or 16. p

In conduits 26 and 28 are fluid attachment walls 25 and 27. The attachment walls provide the splitter stage 10 with memory so that once flow is established in either of conduits 26 and 28, it will remain until intentionally shifted. in communication with conduits 26 and 28 are vents 30 and 32 which provide isolation for the splitter stage, allowing it to be unaffected by pressure changes downstream in the output stage 12.

The vents 30 and 32 also prevent the occurrence of significant circulating flow in passages 26 and 28. If pressure builds up in passage 26 or 28, it could conceivably cause unintentional destruction of the memory of the splitter stage 10. This could lead to an undesirableoscillating of the output stage. I have also found that circulating flow in passages 22 and 24 and in circulating flow passages 26 and 28 could also cause oscillation of the output stage. The vents 30 and 32, therefore, serve to prevent oscillation of the output caused by either of I conduits 22, 24, 26, and 28, input passage 42, and fluid interaction area 40 form a portion of the output stage 12 of the fluidic flip-flop device according to my invention. Conduits 44 and 46 complete the output stage 12. The conduits 22, 24, 26, and 28 form control passages which,

in cooperation with the input supply source P will control which of the two output passages, 44 or 46, the fluid issuing from passage 42 will flow through. Vents 48 and 50 serve to isolate the output stage 12 from pressure changes which may occur downstream of it. The output stage 12 is, essentialy, a bistable fluidic flip-flop having a memory capability associated therewith.

The operation of the device is as follows. When the supply pressure P is activated, an output will appear in either output passage 44 or output passage 46. Assuming the output is in passage 44, a circulating flow is established through passages 22 and 24 from the non-attached control port side, up through the splitter stage and to the low pressure region on the attached side of the output stage 12, i.e., counterclockwise. This Occurs because the fluid flow through passage 44 tends to aspirate the passages 22 and 26. Because of the isolation provided by vents 30 and 32, the circulating flow in passages 26 and 28 is negligible, preventing the output stage from oscillating since a circulating flow in both pairs of passages 22, 24, and 26, 28 would be suflicient to cause the output stage to oscillate. The vents 30 and 32 further assist in preventing oscillation by making the splitter stage 10 load insensitive since loading, in the absence of vents, could destroy the memory of the splitter stage 10 and force oscillation.

An incoming count signal in passage 18 will tend to flow through passage 26 because of the circulating flow from passage 24 to passage 22, thereby causing the output signal to switch to output passage 46. The circulating flow causes incoming signals in passage 18 to have a preference between the two available passages 26 and 28. At this time, the pressure differential across the control ports of the output stage 12 is reversed and the circulating flow also reverses. The incoming signal will continue through passage 26 because the circulating flow will not be sufficient to switch the count pulse away from the attachment wall 25. This attachment wall gives the splitter stage 10 a memory capability. If, at this time, the signal is removed from passage 18, the output remains in output passage 46. A reappearance of a count signal in passage 18 will result in a control signal appearing in passage 28, again due to the circulating flow which will switch the output signal of the output from output passage 46 to output passage 44, thereby changing the state of the output stage. If, at the time, a count signal is being supplied by passage 18 and the output has already been switched from output passage 46 to output passage 44, a pressure pulse is supplied at input passage 14, the memory of the splitter stage will be destroyed, the flow of fluid will switch from passage 28 to passage 26, and the output of the output stage 12 will be switched from the output passage 44 to output passage 46. If, however, the output were already in passage 46, thereby indicating fluid flow in passage 26, the application of a pressure pulse in input passage 14 would not affect the output stage 12, since it would not aflect the attachment at wall 25. If, at the time, no count signal is present in the count passage 18, the application of a pressure pulse in passage 14 will cause a control signal to appear in passage 22 which will cause the output of the output stage 12 to be in passage 46, provided there is a fluid pressure in passage 42. From this, it is apparent that depending on the presence or absence of a flow in passage 42, the output of the output stage can be set by merely the application of a pulse at the proper input passage of the splitter stage 10, whether or not a count signal is present in input passage 18. That is to say that the output will appear in passage 46 whenever a signal is applied in passage 14 provided only that fluid is flowing in passage 42.

For the purposes of this description, various passages have been termed set and reset passages. Because the flipflop according to the present invention is symmetrical, these terms may be interchanged without aifecting the operation of the flip-flop. The symmetry of the device also permits the operational description to be equally applicable to output in either of passages 44 and 46 and control flow in either of the input passages 14 and 16.

Since the splitter stage 10 must be provided with memory, the addition of controls to change the state of the output stage 12 at the ouput stage would no be practical because the memory of the splitter stage would not be affected. These controls must, therefore, be situated upstream of the output stage 12, i.e., at the splitter stage 10. In order to achieve the test or reset function regardless of the condition of the count, means are provided in the form of pair of channels 26 and 28, as well as passages 22 and 24, to control the output of the output stage 12 in such a manner that the application of a set (or reset) pulse in either of control passages 14 or 16 will result in the output appearing at the selected output leg 44 or 46 regardless of the condition of the count on the output of the ouput stage prior to the set (or reset) pulse. In order to prevent oscillation of the flip-flop, either because of pressure build-up overly strong circulating flows, the vents 30 and 32 are provided in passages 26 and 28.

I claim:

1. A fluid device comprising:

means for receiving a fluid signal;

first passage means forming a first pair of channels into which the fluid signal may flow;

first control means for selectively directing the fluid signal into one or the other of said two channels in response to control fluid flow;

second passage means in an intercepting relationship with said first control means for receiving said control fluid in the absence of a fluid signal;

means for receiving a pressurized source fluid;

third passage means forming a second pair of channels into which the source fluid may flow;

the outlets of said first pair of channels forming second control means operative when receiving a fluid signal to selectively direct said source fluid into one or the other of said two channels of said third passage means;

the outlets of said second passage means forming third control means operative when receiving said control fluid flow to selectively direct said source fluid into one or the other of said two channels of said third passage means; and

memory means establishing a preferred channel of said first pair of channels into which said fluid'signal will flow when said source fluid flow remains uninterrupted.

2. The device as claimed in claim 1 including isolation means in association with said first and third passage means.

3. A symmetrical fluid device comprising:

a first fluid means having a bifurcated first passage means for receiving a first fluid flow;

a first control means in communication with said first fluid means for selectively providing a fluid signal for causing said first fluid flow to select one of said bifurcations of said first passage means;

a second fluid means having a fluid interaction region and a bifurcated second passage means for receiving said first passage means in communication with said fluid of said second fluid means interaction region for selectively causing said second fluid flow to select one of said bifurcations of said second passage means;

third passage means in an intercepting relationhip with said first control means and having outlets in communicaiton with said fluid interaction region for sensing a differential pressure across said fluid interaction region and imposing said sensed diiferential pressure on said first fluid flow;

said imposed sensed pressure differential operative to establish in said first fluid flow a preference for one of said bifurcations of said first passage means in the absence of a fluid signal from said first control References Cited P 3 and UNITED STATES PATENTS said third passage means operative in the absence of said first fluid flow to receive a fluid signal from said 3,219,271 11/1965 Bauer 235-201 first control means and to direct said signal toward 5 31277913 10/1966 FOX said second fluid flow to cause said second fluid flow 3,378,197 4/1968 f fi 235201 to select one of said bifurcations of said second pas- 3,443,574 5/ 1969 Posmgles 137-81e5 sage means.

4. The device as claimed in claim 3 including fluid RICHARD WILKINSON, Primary Examiner memory means in said first passage means to maintain 10 L, R, FRANKLIN, A i t t E i said first fluid flow in one of the bifurcations of said first passage means in the absence of a fluid signal from said US. Cl. X.R. first control means. 13781.5 

